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Abstract:
Abstract: Previous EEG studies demonstrated that the two
major word classes, content (open-class) words and function
(closed-class) words are processed differently by healthy humans:
Function words are more lateralized to the left hemisphere than
content words (Neville et al., 1992; Pulvermüller et al.,
1995). According to recent theories on schizophrenia, we
hypothesized that schizophrenic patients would show a reduced
lateralization for function words in EEG parameters. In a lexical
decision task, content words, function words and pronounceable
pseudowords were visually presented. Normals (n=12) and
schizophrenic patients (n=12) had to decide whether a stimulus was
a word or a pseudoword. Evoked potentials were recorded from 64
electrodes. In the time window between 180-260 ms post stimulus
onset function words elicited significantly more negativity above
the left hemisphere, whereas content word processing did not lead
to hemispheric differences. In schizophrenics these word class
differences were not observed. In patients, neither function nor
content words were lateralized to the left hemisphere. The results
replicated the finding of distinct cortical processing of the two
major vocabulary classes in normals. Consistent with the theory of
reduced functional asymmetry in schizophrenic patients, we did not
find differences in lateralization patterns of these word classes
for schizophrenics. We conclude that left hemispheric contribution
to the processing of distinct vocabulary classes in schizophrenic
patients is less pronounced than in healthy controls.
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